Pilocytic astrocytoma is a rare type of brain tumor that occurs mostly in children and young adults under age 20. The tumor rarely occurs in adults. In children, the condition may be called juvenile pilocytic astrocytoma.
Pilocytic astrocytoma gets its name because the tumor originates from star-shaped cells in the brain called astrocytes. Astrocytes are glial cells, which help to protect and sustain brain cells called neurons. Tumors that arise from glial cells are collectively referred to as gliomas.
A pilocytic astrocytoma is most commonly found in a part of the brain called the cerebellum. They can also occur near the brainstem, in the cerebrum, near the optic nerve, or in the hypothalamic region of the brain. The tumor is typically slow-growing and doesn’t spread. That is, it’s considered benign. For this reason, pilocytic astrocytomas are typically categorized as grade I on a scale from I to IV. Grade I is the least aggressive type.
A pilocytic astrocytoma is a fluid-filled (cystic) tumor, and not a solid mass. It’s often successfully removed by surgery, with an excellent prognosis.
Most symptoms of pilocytic astrocytoma are related to increased pressure in the brain, or increased intracranial pressure. These symptoms include:
- headaches that are worse in the morning
- changes in mood or personality
Other symptoms vary depending on the location and size of the tumor. For example:
- A tumor in the cerebellum may cause clumsiness or weakness, because the cerebellum is responsible for controlling balance and coordination.
- A tumor pressing on the optic nerve may cause vision changes, such as blurry vision or involuntary rapid eye movements, or nystagmus.
- A tumor in the hypothalamus or pituitary gland may affect a child’s growth, stature, behavior, and hormones, and cause premature puberty, weight gain, or weight loss.
Causes and risk factors
Gliomas are a result of abnormal cell division in the brain, but the exact cause of this abnormal cell division isn’t known. It’s rare for a brain tumor to be genetically inherited, but certain types of pilocytic astrocytomas, such as optic gliomas, have been associated with a genetic disorder known as neurofibromatosis type 1 (NF1).
The incidence rate of pilocytic astrocytoma is very low. It’s estimated to occur in just 14 out of every 1 million children younger than 15 years of age. The tumor occurs in equal rates in boys and girls.
At the current time, there is no known way to prevent or reduce the risk of a pilocytic astrocytoma in your child. More research is needed to understand the factors that may result in this type of cancer.
How is pilocytic astrocytoma diagnosed?
A pilocytic astrocytoma is usually diagnosed when a doctor or pediatrician notices certain neurological symptoms in a child. A doctor will conduct a complete physical exam and may send the child to a neurologist for further examination.
Additional testing may include the following:
- MRI scan or CT scan to produce images of the brain, either of which may be done with or without contrast, a special dye that helps doctors see some structures more clearly during the scan
- X-ray of the skull
- biopsy, a procedure in which a small piece of the tumor is removed and sent to a laboratory for testing
Treating pilocytic astrocytoma
In some cases, no treatment is required. A doctor will monitor the tumor with regular MRI scans to make sure it doesn’t grow larger.
If the pilocytic astrocytoma is causing symptoms or a scan shows that the tumor is growing, a doctor may advise treatment. Surgery is the treatment of choice for this type of tumor. This is because total removal (resection) of the tumor is often curative.
The objective of surgery is to remove as much of the tumor as possible without harming any part of the brain. The surgery will likely be performed by a skilled neurosurgeon with experience treating children with brain tumors.
Depending on the particular tumor, the neurosurgeon may elect to do an open surgery, where a piece of the skull is removed to access the tumor.
Radiation treatment uses concentrated radiation beams to kill cancerous cells. Radiation may be needed following surgery if the surgeon couldn’t remove the entire tumor. However, radiation isn’t recommended for children under the age of 5 because it can affect brain development.
Chemotherapy is a strong form of chemical drug therapy that destroys rapidly growing cells. It may be needed to stop the growth of the brain tumor cells, or it may be done in conjunction with radiation to help lower the dose of radiation needed.
Juvenile vs. adult pilocytic astrocytoma
Relatively little is known about pilocytic astrocytomas in adults. Less than 25 percent of pilocytic astrocytomas occur in adults older than 20. Similar to juvenile tumors, treatment in adults typically involves surgery to remove the tumor. When a pilocytic astrocytoma occurs in adults, it’s more likely to be aggressive and more likely to recur again after surgery.
In general, the prognosis is excellent. If the tumor is completely removed by surgery, the chances of being “cured” are very high. Pilocytic astrocytoma has a five-year survival rate of over 96 percent in children and young adults, which is one of the highest survival rates of any brain tumor. Pilocytic astrocytomas that occur in the optic pathway or hypothalamus have a slightly less favorable prognosis.
Even if surgery is successful, that child still has to have periodic MRI scans to ensure that the tumor doesn’t return. Recurrence rates are low if the tumor is completely removed, but if the tumor does come back, the prognosis is still excellent after a second surgery. If chemotherapy or radiation was used to treat the tumor, a child may experience learning disabilities and impairments in growth because of the treatment.
In adults, the outlook is also relatively good, but survival rates have been shown to decline with age. One study found that the five-year survival rate was just 53 percent in adults over the age of 60.